1. Epidemiology Branch (S.M.Z., E.M.M., L.A.S., S.L.M., K.C.S., E.F.S.), Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Rockville, Maryland 20854
2. Program in Reproductive and Adult Endocrinology (S.M.Z., A.H.D.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland 20982
3. Department of Obstetrics and Gynecology (R.M.S., J.B.S.), University of Utah and Intermountain HealthCare, Salt Lake City, Utah 84111
4. Department of Statistics (N.G.), University of Haifa, Haifa 3498838, Israel
5. Department of Family, Community, and Rural Health (M.V.W.), The Commonwealth Medical College, Scranton, Pennsylvania 18509